DESCRIPTION: Chronic wounds are an enormously costly worldwide health concern that causes nearly 80,000 lower leg amputations annually in the U.S. alone and is associated with an increased likelihood of death. Strategies to encourage improved repair would impact both quality of life and mortality rates, yet myriad cellular and pathophysiological abnormalities continue to produce severely limited healing incidences with standard therapies. Promising therapeutic alternatives include the application of cellular scaffolds, topical growth factors (GF), or combination wound dressings. However, the incidence of complete closure remains strikingly low and GF delivery strategies largely fail to provide a sufficient quantity of GF to stimulate robust cellular responses. Additional concerns include the need for high GF doses as well as construct escape/off- target effects. New strategies to stimulate efficient and localized production of GFs in situ, by cells involved in active tissue repair, would offer a provocative approach to overcome these difficulties. Thus, we detail an innovative strategy to improve control over the dynamics and location of GF delivery by harnessing ECM remodeling to stimulate GF gene release and expression. In particular, we will exploit our expertise in designing collagen-mimetic peptide (CMP) nanostructures to engineer DNA polyplex-modified collagen scaffolds that induce localized, high efficiency GF expression coordinated with tissue repair kinetics. Our prior studies show that CMP linkage retains polyplexes for over a month in collagen and preserves gene activity in serum. In vivo model gene transfer was significantly enhanced by the CMP modification, and the duration of expression could be easily tuned for periods of a few days to multiple weeks. Moreover, CMP/polyplex/collagens only released polyplexes during collagen turnover, and the freed polyplexes were linked to collagen fragments that appeared to hijack natural endocytic collagen processing pathways. The ability to maintain stable gene depots should provide key reductions in dosing and limit construct escape in slow-healing chronic wounds. Meanwhile, on-demand release and expression is ideally suited to the uncoordinated repair processes that are a hallmark of the chronic wound environment. We will produce CMP/polyplex-modified collagens and will determine whether CMP linkage enhances retention within wound sites and stimulates the simultaneous processing of polyplexes with bioactive ECM fragments. We will elucidate key design parameters controlling polyplex retention, CMP/polyplex/collagen processing, and gene transfer, and will clearly link enhanced gene transfer efficacy to improved activity of GFs such as PDGF. Finally, we will use murine and rabbit wound repair models to test the ability of the PDGF gene product to enhance granulation tissue formation and increase the speed and efficacy of wound repair. These approaches will ultimately be useful as a versatile biomaterials platform able to stimulate improved healing in chronic wounds and a variety of other regenerative medicine applications.